1. Field of Invention
The present invention pertains to a measurement device which is generally known as a dynamometer. A dynamometer is a device for measuring force, torque, work, or mechanical power. The specific dynamometer disclosed herein is a device which has a means which is responsive to a load, the means being capable of measuring the tautness of a line. The device has a means for sensing the deflection of an element. The device also has an elastic deflecting member. Furthermore, the device of the present invention senses the deflection of the elastic member and converts the signal from the sensing means into an electric current or voltage.
2. Description of the Prior Art
Three U.S. patents disclose subject matter which, with respect to the present invention, is the closest prior art of which applicants are aware. These three patents are U.S. Pat. No. 3,526,129 (to Anderson), U.S. Pat. No. 3,444,731 (to Nieuweboer), and U.S. Pat. No. 3,240,281 (to Schaevitz). These three patents are discussed in detail below. Applicant is aware of several other U.S. Pat. Nos. which are related to the present invention, including: 3,060,370; 3,376,740; 4,130,014; 4,326,424.
U.S. Pat. No. 3,526,129, to A. Anderson, discloses a device for measuring tensile forces. The device includes both upper plate sections (4 and 5) and lower plate sections (1 and 2). The upper plate sections are parallel to the lower plate sections. The upper plate sections are connected to the lower plate sections by:
(a) four resilient members (7); and
(b) an assembly which is comprised of: two rigid members (8) and (9) which are bolted to the upper plate sections, the two rigid members having two bolt-like members (12 and 13) threaded therethrough, the bolt-like members in turn contacting a first support (14), the first support (14) in turn being bolted to the upper ends of a pair of arms (15 and 16), on which are arranged a pair of magnetoelastic transmitters (18), the lower ends of the arms (15 and 16) being bolted to a second support (17), the second support in turn being bolted to the lower plate sections.
Although Anderson discloses neither the detailed structure of each of the parts nor a detailed description of the movements of the parts during operation of the device, several facts are apparent upon careful analysis of the Anderson patent by one of skill in the art:
(1) the two arms (15 and 16) extend through the magnetoelastic transmitters--Anderson even implies this in (b) above.
(2) The bolt-like members 12 and 13 must slide against the support 14 during functioning of the resilient rods 7 due to the force exerted perpendicular to the plates 1, 2, 4, and 5. If the bolt members did not slide, the resilient members (7) would not deform because of the rigid connection between the lower plates 1 and 2 and the upper plates 4 and 5 via path (b) described above.
The instant invention differs from Anderson in several ways. Most importantly, in the instant invention, the force which is exerted upon the article-contacting means moves the traveling member a distance X which, absent damping, is substantially proportional to the amount of force f necessary to deform applicant's resilient members enough for applicant's traveling member to move a distance X. In contrast, Anderson's device requires much greater force than that force which is required to simply deform Anderson's resilient rods 7. In fact, Anderson's device does not have any significant "side-to-side" movement because Anderson has a rigid side-to-side linkage occurring from parts 4 and 5 through parts 8 and 9, through parts 12 and 13, through 14, through 15 and 16, through 19, through to 1 and 2. Furthermore, Anderson's device requires substantial side-to-side rigidity because the magnetoelastic sensors operate with a range of motion of only a few thousandths (i.e. less than 0.005 inches) of an inch at most. In Anderson's device, the force required to move the upper plate a distance X "sideways" is much greater than the force required to deflect Anderson's springs (7) sideways by that amount. In fact, Anderson's device will not even move sideways any significant amount. Anderson's springs act as thin columns which buckle under load. In addition, Anderson uses a completely different type of sensor from applicant's, and Anderson does not disclose that his leaf springs are fixedly secured to the upper and lower plate sections, as applicant requires his connecting members to be.
U.S. Pat. No. 3,444,731 to Nieuweboer discloses a "parallelogram-shaped linkage" which is "attached to (a) base". The Nieuweboer device utilizes "flexural pivots" which are spring-loaded. Additionally, the Nieuweboer device utilizes a Hall effect sensor for sensing a change in position of one of the rigid linkage arms with respect to the base of the device. In contrast, Applicant's device utilizes not a parallelogram linkage but a parallelogram-shaped device, the difference being that Nieuweboer utilizes his parallelogram to "link" a first portion of the sensor with a second portion of the sensor, the second portion being in a position which is independent of the parallelogram, whereas applicant's device has a sensor completely within a parallelogram, applicant's device sensing a change in the angles by measuring a change in position of one side of the parallelogram with respect to the opposite side of the parallelogram. Thus, applicant's device has fewer moving parts than Nieuweboer. Applicant's connecting members allow for essentially "frictionless" movement of the traveling member, while Nieuweboer's "flectural pivots" undoubtedly must be more complex and more costly.
U.S. Pat. No. 3,240,281 to Schaevitz discloses a balance which employs ". . . a parallelogram adapted to be moved about the rigidly mounted member 12. The outer member 14 is physically connected to the mounted member 12 through flexure elements 32 and 34". Thus Schaevitz has a parallelogram and he utilizes at least 6 flexural elements similar to applicant's leaf springs. However, Schaevitz discloses a two-piece sensor, a first piece being fixed to one side of the parallelogram and a second piece being fixed to a "mounted member". In contrast, applicant's device has the sensor mounted within the parallelogram. In addition, Schaevitz requires all four sides of the parallelogram to move, whereas applicant's device allows only three sides of the parallelogram to change position.